Resonance raman spectra of the overcooled laser-induced Al plasmas

Resonance Raman spectra of the overcooled laser-induced Al plasmas were studied using an optical parametric oscillator (OPO) wavelength-tunable laser (215-2550 nm, 6 ns) as the re-exciting source. Q-switched neodymium yttrium-aluminum-garnet (Nd:YAG) laser pulses (532 nm, 6 ns) with a laser fluence of 20 J/cm² were used to generate plasmas from an Al alloy target. The laser fluence of the OPO wavelength-tunable laser was around 0.5 J/cm². After tens of microseconds of the plasma generation, the Raman spectra were obtained with a series of wavelengths in between 300 and 322 nm. The Raman spectra of AlO radicals were clearly observed, which showed that the laser-induced Al plasmas interacted with the oxygen in the surrounding air and AlO radicals were produced. Temporal evolutions of the Al, O atoms, and AlO radicals were investigated by laser-induced breakdown spectra and Raman spectra with different time delays. The chemical dynamics of the laser-induced Al plasmas was summarized.